This invention relates broadly to engine control systems and more specifically to a novel control system for controlling engine spark timing. A system incorporating principles of the present invention, when used in conjunction with an internal combustion engine operating at a leaner fuel-air ratio (17-18:1, for example) than is presently customary in production automobile engines, has the potential for significant reductions in exhaust emissions while at the same time improving the fuel economy. Moreover, a system incorporating the present invention can potentially eliminate from the automobile a number of anti-pollution devices which have heretofore been essential to achieving lower exhaust emission levels.
Governmental regulations promulgated over the past few years have had a prominent impact on the American automobile industry, the most prominent impact perhaps being in the area of exhaust emissions. While few if any would quarrel with the admirable objective of having a totally pollution-free atmosphere, there is, because of economic and political considerations, considerable difference of opinion as to how best to work toward achieving this ultimate goal. Generally speaking, the trend has been to mandate increasingly reduced levels of vehicle exhaust emissions from year to year. Heretofore, the only available technology for securing compliance with mandated standards was in the form of anti-pollution controls and devices added to the basic engine. This anti-pollution equipment includes by way of example, EGR systems, catalytic converters, etc. and has greatly added to the basic cost of an automobile. Furthermore, a point of diminishing returns has clearly been reached with existing technology. Prospective regulations are even more stringent and the present state of technology offers no ready solution as to how to meet on a mass production basis even lower exhaust emission levels than those already in force.
The problem of achieving compliance with even present regulations, not to mention prospective ones, has been compounded by what is commonly referred to as the fuel crisis. Generally, the inclusion of anti-pollution equipment and devices to meet present regulations has made less efficient use of fuel and has, therefore, reduced automobile fuel economy. This is in addition to the reduction in fuel economy which is occasioned by other governmentally mandated regulations relating to safety and the like. With the advent of the fuel crisis, there is the real possibility that improved vehicle fuel economy will be mandated by regulation, either directly by specific fuel economy legislation or indirectly by an increased fuel tax or an excise tax on less efficient vehicles. Thus, the automobile industry is presented with the task of further reducing emission levels even though a point of greatly diminished returns has been reached and of simultaneously increasing the fuel economy of the automobile.
Many of those who are not directly involved with the automobile industry do not appreciate the problems which the industry faces. While certain ostensibly pre-eminent and learned authorities have publicly stated that prospectively mandated pollution and economy levels are not unreasonable in view of available technology, it is the automobile industry, and not they, which must comply with governmental regulations to remain in business. To date, no one has come forward with an anti-pollution system for an automobile vehicle which can guarantee compliance with prospective government regulations and which is capable of being economically mass produced by the automobile industry without imposing prohibitive costs on the consuming public.
The present invention is directed toward a novel engine control system which offers the potential for achieving compliance with regulations, both present and future, with respect to emission levels and vehicle economy. Moreover, a system according to the present invention offers the capability for achieving compliance with present regulations, and possibly even future regulations, without the use of anti-pollution equipment which is now common place on production automobile vehicles. Indeed, a system operating according to principles of the present invention can achieve compliance with present emission regulations without the use of such presently used anti-pollution devices as EGR systems, catalytic converters, etc. Moreover, in its preferred form, the present invention incorporates an electronic control system which utilizes available electronic circuit components and devices and which is less expensive than systems having catalytic converters, and EGR anti-pollution systems.
Overall, the present invention in its preferred embodiment pertains to an electronic engine spark timing control system in which a number of individual spark timing signals, which are derived from certain variable engine operating parameters depending upon how the engine is being operated and/or upon certain ambient conditions, are algebraically summed together to develop a resultant spark timing signal. The resulting spark timing signal is compared against a sawtooth engine crank angle signal representative of instantaneous engine crank angle and when a predetermined relationship between the two signals is obtained, a spark is generated. Since the resultant timing signal depends upon enging operation and ambient conditions, the time of spark generation is controlled in accordance therewith. One feature of the present invention relates to the provision of a throttle advance signal derived from the engine throttle. Another feature relates to a programmed vacuum advance signal which is developed from the instantaneous magnitude of engine vacuum but also depends upon the duration for which the engine has been operating in selected operating modes. Another feature relates to a break-idle advance signal which provides spark advance when the engine is accelerated from idle. Another feature relates to an engine start advance signal which provides the advance after the engine has been started. Other features relate to the manner in which the foregoing signals are derived and developed and to their cooperation in the overall engine system.